GLACIERS OP PASSAGE CANAL AND BLACKSTONE BAY 369
""a bay about a league and a half wide, and about three miles deep in a south direction, "where it was terminated by a similar boundary of ice and frozen snow as before described reaching from a compact body of lofty frozen mountains to the water's edge." Grant and Higgins infer that this description refers to either Tebenkof or Blackstone Glacier; but neither the text nor the map seem to us to harmonize with this inference.
None of the later explorers described a tidal glacier in this bay and it has no tidal glaciers at present and is free from floating ice. Three glacial streams flow into Coch-rane Bay from the western side: (1) a stream from the eastern lobe of Tebenkof Glacier; (2) one from a small glacier in the mountains between the Tebenkof valley and Cochrane Bay; and (3) one from the larger Rainy Glacier (Fig. 55), which extends northeastward from the snowfields near the head of Tebenkof Glacier.
Near the mouth, at least, Cochrane Bay has thick mature forest, but since we did not see the conditions near the head, we do not know whether there is such young vegetation as to support the theory of a tidal glacier having retreated southward more than eight miles since 1794. The divide between Cochrane Bay and Port Nellie Juan is said by Grant to be less than 200 feet high, making it clear that when the Port Wells and Passage Canal ice tongues filled Cochrane Bay with ice the expanded glacier spilled over southward into the Port Nellie Juan fiord.
Culross Passage, a narrow, crooked channel east of Cochrane Bay, extends southward from Passage Canal to Port Nellie Juan. It is nearly 11 miles long and from a few hundred feet to a mile wide. There is a branch inlet 2$ miles long on the western side. Culross Island, forming the eastern side of Culross Passage, rises to a height of 1 or 2 thousand feet, and the mainland on the west is even higher, but the passage is not fiord-like, having gradually-sloping walls in most places, and in some portions having very low land near its shores.
At one point, however, there are moderately high, precipitous cliffs. About half way through the passage, the soundings show a submerged divide, with depths of 66 to 78 feet, contrasting with depths of 342 and 336 feet at the northern and southern ends, the former hanging 1062 feet above the bottom of Passage Canal. This is interpreted as indicating that most of the Port Wells and Passage Canal ice moved eastward into Prince William Sound, while little ice streamed southward through Culross Passage, which was, therefore, not deepened much and has many unconsumed rock reefs. At the time of Tna>Hnmim glaciation, however, when Passage Canal and Port Nellie Juan were filled with great glaciers, this passage was undoubtedly full of moving ice. As seen from either Passage Canal, Culross Passage, or Port Nellie Juan, Culross Island looks as if it had been completely overridden and rounded at the expanded stage of glaciation.